Cold frames perfect for starting, extending plant harvest

By Ginna Parsons
Daily Journal
TUPELO – If you’re itching to start digging in the soil, but you know it’s a bit early for that, you might want to consider building a cold frame to get a jump-start on the growing season.
“Cold frames are great for starting and extending your harvest,” said Kaye Lyle, manager of Building Blocks, a charitable arm of the Learning Skills Center in Tupelo, which trains students to be more successful in school.
Building Blocks sells low-cost new or gently used building supplies that have been donated by builders as well as people in the community who are cleaning out sheds, updating kitchens or remodeling homes. Items housed in the warehouse on Cliff Gookin Boulevard include molding, door pulls, plumbing items, lighting fixtures, ceiling fans, cabinets, flooring and carpet remnants, bricks, doors and windows.
“We never know what we’re going to have,” Lyle said, although old windows are usually plentiful. And with these old windows, Lyle fashions cold frames, and you can too, with these easy steps.
The basics
First, you’ll need an old window with panes intact, and it doesn’t need to be larger than 3-feet, Lyle said. You can find old windows at garage sales, antiques stores, on the side of the road and at salvage stores, such as Building Blocks. Don’t use new windows; they block the sun’s rays.
Once you have your window, you’ll need a frame for it to sit on. This can be four bales of hay or some leftover cinder blocks from a home improvement project. The easiest and cheapest, though, is using 2-by pieces of lumber, such as 2-by-6-inch or 2-by-12-inch, Lyle said.
“Do not use treated wood because the stuff used to treat it will leach into the soil in your cold frame,” she said.
Attach the pieces of lumber together with nails or screws to form a frame.
“If you screw the pieces of wood together, you can remove the screws and take the wood apart at the end of the season for easier storage,” she said.
Paint the inside and outside of the frame white to reflect light, Lyle said. And make it as airtight as possible. If the lumber doesn’t fit tightly in the corners, use weather stripping or flexible caulk.
“Plants hate drafts,” she said.
You can attach the window to the frame with hinges if you’d like, but that’s not necessary, especially if you plan to move your cold frame around a lot.
Finally, you’re ready to site your cold frame. You’ll want to put it in a sunny spot, facing south.
Why a cold frame?
Cold frames are beneficial all seasons of the year, Lyle said.
In the spring, you can use them to warm up the soil. Put your cold frame out about 10 days before you want to plant, she said.
“They’re also great for getting seedlings hardened off,” she said. “About a week before you’re ready to plant seedlings in the ground, put the pots in the cold frame during the day. After four or so days, start adding them at night.”
If temperatures get too warm outside, say 50 degrees or above, you’ll need to prop the cold frame open for ventilation. In a cold snap, cover the frame with old blankets or a tarp or bags filled with leaves at night, but be sure to remove them first thing in the morning before the sun comes out.
Also, to help keep plants warm at night, you can take plastic milk jugs, paint them with flat black paint, fill them with water and place them in the cold frame during the day. They’ll absorb heat from the sun during the day and release it at night.
In the summer, cold frames can be used to propagate plants from cuttings. In the fall, you can use them to extend the growing season and start cool weather vegetables. And in the winter, if your cold frame is large enough and insulated inside, you could weather plants over like ferns.
“Actually, a cold frame is just a mini-greenhouse,” Lyle said. “You can be very elaborate with them – there are kits that are available – or very economical. If you pay $5 for a window and pick up some old wood from a construction site, you can easily build your frame for less than $15.”
Ginna Parsons is the Daily Journal’s food/home/garden editor.